Structural gene for yeast iso-2-cytochrome c.

Protein analysis and genetic studies have led to the identification of the structural genes of iso-1-cytochrome c and iso-2-cytochrome c, which constitute, respectively, 95% and 5% of the total amount of cytochrome c in the yeast Saccharomyces cerevisiae. The structural gene CYC1 for iso-1-cytochrome c was previously identified by Sherman et al. (1966) and the structural gene CYC7 for iso-2-cytochrome c is identified in this investigation. A series of the following mutations were selected by appropriate procedures and shown by genetic tests to be allelic: CYC7+ →CYC7-1 →cyc7-1-1 →CYC7-1-1-A, etc., where CYC7 + denotes the wild-type allele determining iso-2-cytochrome c; CYC7-1 denotes a dominant mutant allele causing an approximately 30-fold increase of iso-2-cytochrome c with a normal sequence, and was used as an aid in selecting deficient mutants; cyc7-1-1 denotes a recessive mutant allele causing complete deficiency of iso-2-cytochrome c; and CYC7-1-1-A denotes an intragenic revertant having an altered iso-2-cytochrome c at the same level as iso-2-cytochrome c in the CYC7-1 strains. The suppression of cyc7-1-1 with the known amber suppressor SUP7-a indicated that the defect in cyc7-1-1 was an amber (UAG) nonsense codon. Sequencing revealed a single amino acid replacement of a tyrosine residue for the normal glutamine residue at position 24 in iso-2-cytochrome c from the suppressed cyc7-1-1 strain and also in five revertants of cyc7-1-1, of which three were due to extragenic suppression and two to intragenic reversion. The nature of the mutation that elevated the level of normal iso-2-cytochrome c in the CYC7-1 strain was not identified, although it occurred at or very near the CYC7 locus but outside the translated portion of the gene and it may be associated with a chromosomal aberration. Genetic studies demonstrated that CYC7 is not linked to CYC1, the structural gene for iso-1-cytochrome c.     

Effect of somatostatin suppression of glucagon secretion on glucose production in sheep.

The effect of somatostatin (SRIF) on glucagon and insulin secretion was examined in fed and fasted sheep. This was related to changes in glucose production. Infusion of SRIF at 80 micrograms/h caused a marked reduction in plasma glucagon concentrations. However, the insulin response to SRIF infusion was not consistent; its concentrations decreased occasionally, but often did not change. The depression of glucagon was not associated with a significant reduction in blood glucose concentrations in either fed or fasted sheep, but was associated with a reduction in glucose production by 12--15%. The inhibitory effect of insulin on glucose production was not markedly increased by glucagon deficiency. Infusion of insulin at 1.17 U/h with SRIF decreased glucose production only an additional 10%. Thus, it appears that under basal conditions pancreatic hormonal influences on hepatic glucose production were relatively small in sheep. This implies that under normal conditions in sheep, substrate supply has a much greater impact on hepatic glucogenesis than do hormones.     

Reproduction in free-ranging Propithecus verreauxi: Estrus and the relationship between multiple partner matings and fertilization

Female sifaka mate selectively with one or more resident and/or non-resident males during the breeding season. Various adaptive explanations have been advanced to explain why female primates mate with multiple males including that 1) females seek to confuse paternity and thereby forestall male infanticide and/or ensure male infant care or 2) females seek to ensure fertilization. Assessing the power of fertilization insurance to explain mating patterns in females requires information on the temporal relationship between mating and ovarian hormones. The hormonal correlates of reproduction and mating in free-ranging Propithecus verreauxi were investigated using excreted steroids as indices of reproductive state. Solid-phase extraction and radioimmunoassay techniques were used to measure unconjugated estradiol (E₃) and progesterone (P₄) in 485 desiccated fecal samples collected from five female sifaka before and during the breeding season at Beza Mahafaly, Madagascar. Results suggest that behavioral estrus was characterized by 10- to 15-day elevations in E₂; hormonal activity was observed to be similar to pseudo-estrus reported for other lemur species; apparent conception was associated with sustained P₄ elevations beginning 1 to 3 days post-estrus with gestational phase elevations of E₂ beginning 42 to 45 days post-conception; and mating with multiple partners appeared not to be a prerequisite to fertilization, as conception resulted from both monoandrous and polyandrous matings. These preliminary data suggest that fertilization insurance is not adequate to explain polyandrous mating in sifaka at Beza Mahafaly. © 1996 Wiley-Liss, Inc.     

Comparison of the spectra of genetic damage in formaldehyde-induced ad-3 mutations between DNA repair-proficient and -deficient heterokaryons of Neurospora crassa.

The mutagenic effects of formaldehyde (FA) have been compared in DNA repair-proficient (heterokaryon 12) and DNA repair-deficient (heterokaryon 59) two-component heterokaryons of Neurospora crassa. The data from forward-mutation experiments were used to compare the spectra of FA-induced specific-locus mutations at two closely linked loci in the adenine-3 (ad-3) region and on the FA-induced inactivation of heterokaryotic conidia. Previous studies have demonstrated that specific-locus mutations at these two loci result from five major genotypic classes, namely two classes of gene/point mutations (ad-3A(R) and ad-3B(R)), and three classes of multilocus deletion mutations ([ad-3A](IR), [ad-3B](IR), and [ad-3A ad-3B](IR)). Genetic analysis of ad-3 mutants recovered from both heterokaryons after FA treatment demonstrates that predominantly gene/point mutations were found in H-12 (93.2% ad-3(R), 6.8% [ad-3](IR)) and a significantly higher frequency of multilocus deletion mutations in H-59 (62.8% ad-3(R), 37.0% [ad-3](IR)). The data from our experiments with FA on H-12 demonstrate and confirm the data from other assays that FA is a weak mutagen in this DNA repair-proficient strain. However, the data from our experiments with the DNA repair-deficient strain H-59 demonstrate that comparable concentrations of FA cause more pronounced inactivation of heterokaryotic conidia and, at the highest concentration tested, about a 35-fold higher frequency of ad-3 mutations. In addition, FA induced a 5.4-fold higher frequency of ad-3 mutations resulting from multilocus deletion mutation in H-59 than in H-12. Based on our earlier studies with X-ray-induced multilocus deletion mutations, it is this class of FA-induced ad-3 mutations that might be most expected to show deleterious heterozygous effects. The implications of the present data base from our experiments with Neurospora are that the mutagenic (and possibly the carcinogenic) effect of FA exposure might well vary in different human population subgroups.     

Reproductive Behavior of Female Propithecus verreauxi at Beza Mahafaly,Madagascar

Prosimian and anthropoid females are generally thought to have divergent reproductive patterns, characterized by circumscribed and situation-dependent receptivity. This dichotomy underpins the traditional view that nonreproductive mating serves a social function in anthropoid females, distinguishing them from prosimians which, like most other mammals, mate only when conception is most probable. Circumscribed estrous cycles differ from anthropoid menstrual cycles by the presence of menstruation, and greater flexibility in timing and longer duration of receptivity in the latter. The degree to which sexual behavior is tightly synchronized to periovulatory events in Propithecus verreauxi was assessed via the behavioral, hormonal, and social correlates of reproduction in a free-ranging population. I collected data from two social groups before and during the 1990–1991 and 1991–1992 breeding seasons at Beza Mahafaly, Madagascar. I also conducted 644 focal-animal hours and collected 485 fecal samples from five marked females in the Vaovao and Vavy Masiaka social groups. Estrus was behaviorally characterized by 0.5–96-h periods of receptivity when females were motivated and willing to mate, the latter not always coincident with periovulatory events. Females exhibited age- and rank-related asynchronous receptivity, and in some cases, periovulatory synchrony within groups. Sifaka were not pair-bonded. Most females mated with multiple males, temporally ordering partners based on male residence and age. Mating was limited by male mate-guarding and sexual aggression by males, female mate competition, and aversions to mating with certain partners. It was facilitated by surreptitious copulations, positive mate choice, and the availability of non-resident mating partners.     

Role of peroxynitrite in altered fetal-placental vascular reactivity in diabetes or preeclampsia

Oxidative stress may increase production of superoxide and nitric oxide, leading to formation of prooxidant peroxynitrite to cause vascular dysfunction. Having found nitrotyrosine residues, a marker of peroxynitrite action, in placental vessels of preeclamptic and diabetic pregnancies, we determined whether vasoreactivity is altered in these placentas and treatment with peroxynitrite produces vascular dysfunction. The responses of diabetic, preeclamptic, and normal placentas to increasing concentrations of the vasoconstrictors U-46619 (10(-9)-10(-7) M) and ANG II (10(-9)-10(-7) M) and the vasodilators glyceryl trinitrate (10(-9)-10(-7) M) and prostacyclin (PGI(2); 10(-8)-10(-6) M) were compared as were responses to these agents in normal placentas before and after treatment with 3.16 x 10(-4) M peroxynitrite for 30 min. Responses to both vasoconstrictors and vasodilators were significantly attenuated in diabetic and preeclamptic placentas compared with controls. Similarly, responses to U-46619, nitroglycerin, and PGI(2), but not ANG II, were significantly attenuated following peroxynitrite treatment. The presence of nitrotyrosine residues confirmed peroxynitrite interaction with placental vessels. Overall, our data suggest that peroxynitrite formation is capable of attenuating vascular responses in the human placenta.     

Sphingomyelin interfacial behavior: the impact of changing acyl chain composition

Sphingomyelins (SMs) containing homogeneous acyl chains with 12, 14, 16, 18, 24, or 26 carbons were synthesized and characterized using an automated Langmuir-type film balance. Surface pressure was monitored as a function of lipid molecular area at constant temperatures between 10 degrees C and 30 degrees C. SM containing lauroyl (12:0) acyl chains displayed only liquid-expanded behavior. Increasing the length of the saturated acyl chain (e.g., 14:0, 16:0, or 18:0) resulted in liquid-expanded to condensed two-dimensional phase transitions at many temperatures in the 10-30 degrees C range. Similar behavior was observed for SMs with lignoceroyl (24:0) or (cerotoyl) 26:0 acyl chains, but isotherms showed only condensed behavior at 10 and 15 degrees C. Insights into the physico-mechanical in-plane interactions occurring within the different SM phases and accompanying changes in SM phase state were provided by analyzing the interfacial area compressibility moduli. At similar surface pressures, SM fluid phases were less compressible than those of phosphatidylcholines with similar chain structures. The area per molecule and compressibility of SM condensed phases depended upon the length of the saturated acyl chain and upon spreading temperature. Spreading of SMs with very long saturated acyl chains at temperatures 30-35 degrees below T(m) resulted in condensed films with lower in-plane compressibilities, but consistently larger cross-sectional molecular areas than the condensed phases achieved by spreading at temperatures only 10-20 degrees below T(m). This behavior is discussed in terms of the enhancement of SM lateral aggregation by temperature reduction, a common approach used during domain isolation from biomembranes.     

Real-time measurement of solute partitioning to lipid monolayers

The interaction of a peripheral protein with a lipid-water interface can show a pronounced dependence on the composition and two-dimensional packing density of the lipids that comprise the interface. We report a novel optical method for measuring the adsorption of macromolecules, such as proteins and nucleic acids, and smaller solutes, such as drugs, to lipid monolayers at the gas-liquid interface. Using fluorescence emission from proteins and a small molecule, we demonstrate that the emissions from these solutes when in the aqueous phase and when associated with the monolayer can be temporally separated. Such separation allows measurement of the extent of solute adsorption, spectral characterization of the adsorbed solute, and characterization of lipid organization using adsorption kinetics. The method does not require, but is compatible with, the solute having different spectral properties in the bulk and surface phases. Indeed, if optical signals from adsorbed and soluble solute are the same or their relationship is known, absolute surface excess of adsorbed solute can be calculated without independent calibration. With appropriate instrumental configuration, the method should be adaptable for screening solutes for interaction with planar monolayers having both well-defined composition and adjustable lipid packing density.     

Interspecific variation of body shape and sexual dimorphism in three coexisting species of the genus <Emphasis Type="Italic">Petrotilapia</Emphasis> (Teleostei: Cichlidae) from Lake Malawi

Differences in color patterns have been the most used feature in describing cichlid species belonging to genus Petrotilapia from Lake Malawi. In this study, we quantified morphological variation in body shape within and among three coexisting Petrotilapia species using landmark-based geometric morphometric methods. Statistic analyses revealed significant body shape differences among species but not between sexes. Post hoc multiple comparisons based on Mahalanobis distances revealed that P. nigra was significantly different from P. genalutea and Petrotilapia sp., whereas the latter two were not significantly different. The splines generated showed that the most pronounced variation was in the head region, in which P. nigra had a relatively longer and deeper head than the other two. The most clear-cut distinction was in gape length; P. genalutea had the longest gape, followed by Petrotilapia sp., whereas P. nigra had the shortest gape. Body depth was shallower in P. nigra than the others. When comparing sexes by their centroid size, ANOVA revealed that males were bigger than females. Therefore, we conclude that color is not the only feature that can distinguish these congeners. We discuss the observed sexual dimorphism in terms of sexual selection and relate morphological variation among species to feeding behavior, which may help explain their coexistence in nature.